1. Have you verified that sending actual MIDI data to the unit over the USB cable from your PC actually triggers a sound? Using any app other than BIAB. Any simple straight GM MIDI file player set to send over the SC-8820 MIDI output?

2. A ".pat" file is/can be accessed via the "higher banks" (aka "+" button). The "+" button is sandwiched between the "GM2 F" buttons and the "Volume" (same row as pan, A.reverb, Tone, Bank0, LSB, ...)

When you click it asks for the Pat file you want to open - then lists the patches, and the associated patch #, MSB and LSB banks. The patch you select will affect/sound on the BIAB instrument (part) you have selected (Bass, Piano, Drums, Guitar, Strings, Melody, or Soloist ) at top of BIAB screen.

It's nice if under "Opt/Midi Audio Driver Setup/ Synthesizer/Sound Card" pull down your synth is there explicitly but for an SC-8820 (I have an 8850) the generic GM instrument or even the "SC-88" should work - at least for first 128 patches to get it started as a basic GM device.

Suggestion after BIAB is up and song is selected, and " Synthesizer/Sound Card" has been set - turn the SC-8820 off then back on - just to ensure a "clean slate" on the unit.

Good luck
Larry

Win10Pro,i9,64GB,2TBSSD+20TBHDDs,1080TI,BIAB'24,Scarlett18i8,Montage7,Fusion 8HD,QS8,Integra7,XV5080,QSR,SC-8850,SPLAT,FL21&others,Komp.14,IK suite&others, just a guitar player-AXE FX III &FM9T, FishmanTP, MIDIGuitar2, GK2/3'sw/GI20